Modern pollen distribution as related to vegetation communities and elevation in the Grand Canyon, Arizona
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Authors Sigleo, Wayne R.
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Link to Item http://hdl.handle.net/10150/566376 MODERN POLLEN DISTRIBUTION AS RELATED TO
VEGETATION COMMUNITIES AND ELEVATION
IN THE GRAND CANYON, ARIZONA
by Wayne Richard Sigleo
A Thesis Submitted to the Faculty of the
DEPARTMENT OF GEOGRAPHY AND AREA DEVELOPMENT
In Partial Fulfillment of the Requirements For the Degree of
MASTER OF ARTS WITH A MAJOR IN GEOGRAPHY
In the Graduate College
THE UNIVERSITY OF ARIZONA
1 9 7 1 STATEMENT BY AUTHOR
This thesis has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.
Brief quotations from this thesis are allowable with out special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholar ship. In all other instances, however, permission must be obtained from the author.
SIGNED: U W i r
APPROVAL BY THESIS DIRECTOR
This thesis has been approved on the date shown below:
2 / PAUL S . MARTIN Date Professor of Geosciences ACKNOWLEDGMENTS
I wish to express my appreciation to Drs. Paul S.
Martin and Richard W. Reeves of The University of Arizona for their inspiration, assistance, and guidance throughout this study.
I am much indebted to Mr. James E. King and Dr. A.
L. Solomon of The University of Arizona for criticism, helpful suggestions, and certain critical pollen identifica tions during the course of this study.
Gratitude is expressed to Mr. David Oschner of the
United States Park Service, Department of the Interior,
Grand Canyon, Arizona for assistance in the undertaking of this project. I also wish to thank Messrs. Jeff Zauderer and William Lloyd for their assistance in the field work.
Thanks are also expressed to Mr. Len Tavernetti for his assistance in photographing the diagrams in this thesis.
Appreciation is expressed to the Departments of
Geography and Area Development and Geosciences for the use of equipment and facilities necessary to undertake this problem.
A special note of thanks is due my wife, Anne, who followed me into the Canyon.
iii TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS...... v
LIST OF T A B L E S ...... vi
ABSTRACT ...... vii
INTRODUCTION ...... 1
THE PHYSICAL S E T T I N G ...... 5 Physiography...... 5 Climate ...... 7 Vegetation...... 10
METHODOLOGY...... '...... 15 Localities and Sampling Procedure ...... 15 Pollen Extraction ...... 17 Pollen Analysis ...... 17
MODERN POLLEN DISTRIBUTION ...... 22
Analysis...... 22 Consistency of the D a t a ...... 30
SUMMARY AND CONCLUSIONS ...... 33
APPENDIX 1: MODERN POLLEN FREQUENCIES IN THE GRAND CANYON, A R I Z O N A ...... 35
LITERATURE C I T E D ...... 46
iv LIST OF ILLUSTRATIONS
Figure Page
1. The Grand Canyon, Arizona...... 4
2. Map of the Study A r e a ...... 6
3. Modern Pollen Spectra of the Grand Canyon, A r i z o n a ...... 21
4. Relationship of Arboreal Pollen Frequency to Elevation ...... 23
v LIST OF TABLES
Table Page
1. Temperature Data for the Grand Canyon Area . . . 9
2. Extraction Procedure for Southwestern Alluvial Pollen Samples ...... 18
vi ABSTRACT
Twenty-five surface soil samples were collected and analyzed for their pollen content from a traverse across the Grand Canyon, Arizona. In an attempt to relate the modern pollen distribution to the vegetation in the Canyon, five principal vegetation communities were described ranging from a mixed coniferous forest (elev. 2515 m) to a desert shrub community (elev. 760 m) near the Colorado
River.
The modern pollen distribution of most major plant communities is distinctive despite the over-representation of wind-blown coniferous pollen, especially Pirns, at lower
elevations in the Canyon. The woodland and forest communi ties are characterized by greater than 50 percent Pinus pollen. Relatively high frequencies of Compositae and
Ephedra pollen dominate the desert shrub community.
vii INTRODUCTION
An important part of plant geography deals with the variations in vegetation patterns through time. Understand ing the nature of vegetation changes and deducing their causes has been largely dependent on the reconstruction of past plant communities through macrofossil analysis.
Palynology, the study of pollen and spores, is one important tool which can be used in the reconstruction of fossil vegetation.
The nature of past vegetation at a given site can be empirically determined by relating the modern pollen distribution to the vegetation community surrounding the site (Davis, 19695 Martin, 1963)• Once this relationship is understood, changes in the composition of vegetation communities through time may be deduced from the assemblages of pollen grains preserved in the stratigraphic section.
The problem is to establish spatial variations in the surface pollen distribution as related to the vegetation
communities and elevation in the Grand Canyon, Arizona. The
results should provide a basis for the evaluation of glacial
and postglacial pollen records in the Grand Canyon area. In
addition, the results of this study will be compared to other
selected modern pollen studies in the Southwest to determine
the consistency of elevational and zonal associations.
1 2
Several studies comparing the modern pollen distribution with vegetation communities and elevation have been conducted in the Southwest (Adam, 1965J Bent and
Wright, I963; Dixon, 1962; Hevly, 1964; Hevly, Mehringer and Yokum, 19655 Maher, 19633 Martin, 19633 Mehringer, 196?3 Potter and Rowley, i960). Most of these studies were undertaken to establish a modern base for the paleoeco- logical interpretation of fossil pollen data. These studies have described various methods for sampling the modern pollen rain, and all have established some degree of correlation between the surface pollen and the vegetation communities.
The Grand Canyon is an area of high vertical relief
(Figure 1) and the vegetation is characterized by a wide variety of ecological responses. The morphology of the
Canyon suggests a closed depositional basin for pollen derived from source areas at higher elevations. Nearly all previous modern pollen studies have been conducted in relatively open alluvial areas or along traverses over the slopes of mountain ranges. A modern pollen study has never been conducted across such a unique topographic feature as the Grand Canyon.
Four previous palynological studies have been conducted in the general area of the Grand Canyon (King,
19713 Martin, pers. comm.; Martin, Sabels and Shutler, I96I;
Schwartz, Lange and de Saussure, 1958). King's (1971) study 3 consists of a traverse of surface pollen samples collected
along the Colorado River from Lee's Ferry to Diamond Creek,
a distance of 365 kilometers. The study was initiated to provide background data for interpreting fossil pollen profiles in the Canyon. The results indicate the modern pollen distribution closely correlates with changes in
vegetation and geomorphology along the River.
In a study of Tse-an Kaetan Cave in Cremation Canyon,
Anderson in Schwartz et al. (1958) found a high relative abundance of Abies and Picea pollen in the cave sediments, but no radiocarbon control is available. The most sig nificant feature of Martin's fossil data is the high
frequency of Artemisia in deposits dated around 12,000 years B.P. 4
Figure 1. The Grand Canyon, Arizona. THE PHYSICAL SETTING
The Grand Canyon is located in northwestern Arizona approximately 96 kilometers north of the town of Williams, via U.S. Highway 64. The principal area of study is located
in the Grand Canyon National Park, from the area commonly
known as the South Him across the Canyon to the North Rim
(Figure 2).
Physiography
The Grand Canyon is part of the Colorado Plateau,
and is a broad, uplifted asymetrical arch underlain by
highly resistant Permian limestones (Strahler, 1944). The
Grand Canyon gorge was formed by the erosive action of the
Colorado River through thousands of feet of sediment. The
Colorado River has dissected the area into two high, flat
plateaus: the Kaibab, known as the North Rim, and the
Coconino to the south.
The Kaibab Plateau is the higher of the two with an
elevation ranging from 2280-2800 meters. The terrain
generally consists of rounded valleys of gentle slope not
more than 90-120 meters deep.
The Coconino Plateau or South Rim is the southward
extension of the Kaibab Plateau and ranges from 1820-2280
meters in elevation. The Plateau is characterized by very
5 Traverse » .— - Spot Eftvetion’ (meters) Contour Line
Figure 2. Map of the Study Area. 7 little relief and a generally southerly slope. The inner canyon is an area of extremely rugged relief characterized by deep narrow canyons and towering erosional remnants. The
Canyon itself is asymetrical in form with the North Rim being nearly twice as far from the Colorado River as the
South Rim.
In the study area the elevation on the North Rim is about 2530 meters. The South Rim is approximately 2135 meters, and the Colorado River at Phantom Ranch is about
760 meters above sea level. The length of the traverse across the Canyon, via the Bright Angel and North Kaibab trails, is approximately 40 kilometers.
Climate
The average annual precipitation recorded at the
Bright Angel Ranger Station on the North Rim is approx imately 635 millimeters. Average annual precipitation in the Inner Gorge at Phantom Ranch is about 254 millimeters, and the amount at the Park Headquarters on the South Rim is approximately 4o6 millimeters (Green and Sellers, 1964;
Bennett, 1969)•
The greatest amounts of precipitation at the Grand
Canyon are generally received during the summer and winter seasons with the spring and fall being relatively dry.
Summer precipitation is generally derived from locally intense thundershowers. Winter precipitation is usually 8 related to mid-latitude storm cells. At the rims of the
Canyon winter precipitation usually occurs in the form of snow with yearly accumulations of greater than 3*8 meters on the Kaibab Plateau.
A strong temperature gradient exists between the
Canyon rims and bottom (Table 1). The average annual temperature on the North Him is 6.1° C ., with temperatures at the bottom averaging 20.6° C. An intermediate value of
9.4° C. is recorded at the South Rim (Green and Sellers,
1964).
Because of the tremendous variation in relief in the
Canyon, a straight line temperature-precipitation relation ship between the rims and bottom is impossible and estimating intermediate amounts is, at best, hazardous.
Wind information is not available for the Grand
Canyon area; however the highest annual velocities for
Arizona have been recorded at Prescott, Flagstaff, and
Winslow. Flagstaff is the closest recording station to the
Grand Canyon with a general prevailing wind direction from the southwest. The frost free periods in the Grand Canyon area, roughly approximating the plant growing season, are
101 days on the North Rim, 331 days in the Inner Canyon, and
148 days on the South Rim (Green and Sellers, 1964). 9
Table 1. Temperature Data for the Grand Canyon Area.*
South Rim Phantom Ranch North Rim (Elev. 2100 m) (Elev. 760 m) (Elev. 2560 m)
January average 1.7 7.8 3.3
July average 20.6 33-3 16.7
Annual 9.4 average 20.6 6.1
Lowest recorded -28.9 -7.2 -31.7
Highest recorded 36.7 48.9 32.8
^Temperatures are in degrees centigrade. (After Green and Sellers, 1964.) 10
Vegetation
The plant communities in the Grand Canyon range from spruce-fir forests distributed on the higher slopes of the
Kaibab Plateau to a desert shrub community at the lower elevations along the Colorado River. The vegetation com munities in this area of the Grand Canyon have been described by several workers (Bennett, 19695 Clover and Jotter, 1944;
Martin, n.d.; Merkle, 1952; 1954; 1962; Merriam, 1890; Rand,
1958; Rasmussen, 1941). Nearly all of these studies have been conducted on either the North Rim, the South Rim, or the Canyon bottom. Rand (1958) described the vegetation communities across the Canyon, but her study is too broad for palynological interpretations.
In this study the descriptions of the plant communi ties in the Grand Canyon are based on the previously published studies, and the author's observation of the vegetation along the trails across the Canyon. The descrip tions are by no means a complete list of species and were based on apparent local plant dominance. Nomenclature follows Kearney and Peebles (i960).
With increasing elevation five principal plant communities are recognized: desert shrub community (Bennett,
1969; Clover and Jotter, 1941; Martin, n.d.), juniper shrub savannah, pinyon-juniper woodland (Merkle, 1952), oak wood land, and mixed coniferous forest (Merkle, 1962). Other vegetation communities present in this area of the Canyon, 11 but not directly related to the study, include ponderosa pine parkland present at higher elevations on the Coconino and
Kaibab plateaus and a spruce-fir forest distributed above
2650 meters on the North Rim (Merkle, 195^-) •
The desert shrub community is situated below
approximately 1220 meters in the Canyon. The vegetation in
this area is characterized by low, woody species of desert
shrubs (Martin, n.d.). In general the vegetation is
dominated by catclaw acacia (Acacia greggi) and Mormon tea
(Ephedra, sp.) which are commonly found distributed together.
Both JE. nevadensis and 12. torreyana are present in the
desert community. Yucca (Yucca baileyi) and agave (Agave
utahensis) are commonly present with numerous cacti (Opuntia
sp.). Other common shrubs include Fallugia paradoxa, Rhus
sp., Encelia farinosa, and Atriplex sp. The herbaceous
vegetation consists of various grasses, composites, and
legumes.
The vegetation on the Tonto Shelf (elev. 1160 meters)
on the south side of the Canyon is characterized by an
almost pure blackbrush (Coleogyne ramosissima) community
with Yucca, catclaw. Ephedra sp., agave and cacti. Riparian
communities found along the Colorado River and major tribu
taries in this area include cottonwood (Populus fremontii),
willow (Salix sp.), salt cedar (Tamarix pentandra), desert
almond (Prunus fasciculata), and seep willow (Baccharis sp.). 12
Above the desert shrub community is the juniper shrub savannah, which extends to an approximate upper altitudinal limit of 1525 meters on either side of the
Canyon. The community is dominated by two species of juniper (Juniperus utahensis and scopulorum). In addition this community is characterized by a heterogeneous mixture of xerophytes reflecting the low soil moisture and high temperatures of this area (Rand, 1958)• These plants include hoptree (Ptelea pallida), currant (Ribes inebrians), squawbush (Rhus trilobata) and redbud (Cercis occidentalis) and oak (Quercus sp.). Other shrubs include Fallugia paradoxa, Philadelphus microphyllus. Primus fasciculata,
Gutierrezia sp., Chrysothamnus sp., Ephedra sp., Artemisia sp.. Yucca sp.. Agave sp., and Opuntia sp. The herbaceous elements in this community are grasses, small composites, legumes, and mallows. Chenopods are locally distributed in disturbance environments along tributary drains.
The pinyon-juniper woodland is distributed between
1675-2185 meters elevation in this area of the Canyon, but it is best developed between 1830-2135 meters. Merkle (1952) placed the altitudinal range of this community between I98O-
2225 meters on the Coconino Plateau, but the pinyon-juniper association extends well below the South Rim. This com munity also occurs in scattered stands on open and south facing slopes above 2440 meters on the North Rim. 13 The community is composed of pinyon pine (Pinus edulis) and juniper (Juniperus sp.) with varying amounts of gambel oak (Quercus gambelii). Subdominant shrubs consist of Chrysothamnus sp., fernbush (Chamaebatiaria millefolium), and Gutierrezia sp. (Merkle, 1952). Other shrubs present in this community include Ephedra viridis, cliffrose (Cowania mexicana), sagebrush (Artemisia tridentata), and Opuntia sp.
The herbaceous vegetation consists primarily of grasses and small composites. Below the rims of the Canyon other impor tant elements of the pinyon-juniper community are manzanita
(Arctostaphylos sp.), mountain mahogany (Cercocarpus sp.), currant, mahonia (Berberis fremontii), rose (Rosa sp.) and buckbrush (Ceanothus sp.). Douglas fir (Pseudotsuga taxifolia) is locally distributed below the rims on mesic, north-facing slopes.
A ponderosa pine (Pinus ponderosa) community is distributed above 2135 meters on the South Rim and in scattered locations on the North Rim. Merkle (1962) has divided the community into two units: ponderosa pine sagebrush community and ponderosa pine-grassland.
An oak woodland largely replaces the pinyon-juniper association in Roaring Springs Canyon on the north side of the Canyon. This community has an altitudinal range between
1525-2130 meters in this canyon. The oak woodland is a response to apparently more mesic conditions due to cold air drainage in this narrow, northwest trending canyon. The vegetation is characterized by dense stands of gambel oak with varying amounts of hop-hornbeam (Ostrya knowltoni) and
New Mexico locust (Robinia neomexicana). Other shrubs in
this association include silktassel (Garryea flavescens),
buckbrush, cliffrose, Rosa sp., and mahonia. Pinyon pine
and juniper are locally present in this community but are
most abundant at lower elevations and on more zeric south
facing slopes. Ponderosa pine and Douglas fir are locally
present in the oak woodland, and generally confined to
north-facing slopes above 2130 meters elevation. The her
baceous vegetation in the oak woodland consists of abundant
grasses and numerous small compositae.
Above 2880 meters elevation in Roaring Springs
Canyon is a mixed coniferous forest of ponderosa pine, white
fir (Abies concolor), Douglas fir, and aspen (Populus
tremuloides).
The mixed coniferous forest occurs in mesic locali
ties on the North Rim, but is less widely distributed than
the spruce-fir forests which are present at the higher
elevations. Other important woody plants in the mixed
coniferous forest include minor amounts of gambel oak and
New Mexico locust, pygmy juniper (J. communis), hop-hornbeam
and cliffrose. The herbaceous vegetation consists primarily
of grass, small composites and forbs. METHODOLOGY
Localities and Sampling Procedure
Modern pollen samples in the Southwest have been collected from lake sediments, cave fills, moss polsters, atmospheric pollen samplers, and the sediment from cattle tanks. Most of these methods are inapplicable in the Grand
Canyon, and surface soil samples were selected. These samples were used to determine the relation between the modern pollen distribution to vegetation communities and elevation. The field work was conducted during June, 1970; the laboratory processing and analysis were done during the following fall and winter.
Twenty-five surface soil samples were collected along a traverse originating on the South Rim near Grand
Canyon Village and terminating on the North Rim near Bright
Angel Point. The traverse roughly follows the trace of the
Bright Angel fault. All sampling locations were reached via the Bright Angel and North Kaibab trails. Supplementary
surface soil samples were collected at two sites on the
Kaibab and Coconino Plateaus, some distance from the rims of the Canyon.
The soil surface samples within the Canyon were
collected at vertical intervals of approximately 150 meters. The elevation intervals were determined by means of a
15 16
U.S.G.S. topographic map at a scale of 1:62,500, and checked against a pocket altimeter. The sites were selected some distance from the trails to avoid any cultural disturbance in the plant communities and in the surface pollen rep resented. Samples were also collected from areas of exposed ground in an attempt to assess the significance of long distance transport.
To avoid any gross over-representation of a particular pollen species at a site, the surface soil samples were collected using a modified version of the multiple subsample technique (Hevly, Mehringer, and Yokum,
1965)• This method consisted of collecting 10-20 subsamples of surface soil at some interval (5-10 paces), in an area
30-40 meters square. Each subsample consisted of a pinch of surface sediment placed in a clean plastic bag and thoroughly mixed with the other subsamples collected from the site. The above collecting procedure could not always be regidly adhered to, as the number of subsamples, sampling interval, and site area varied due to precipitous conditions in the local terrain.
The general composition of the local dominant # vegetation was noted at each site, and unknown plant species were collected and later identified. No attempt was made to classify the local vegetation by any phytosociological parameters. Slope was measured at each site by means of 17 a clinometer, and other site features such as location, exposure, and general soil characteristics were noted.
Pollen Extraction
The extraction of the surface soil samples was done at the Laboratory of Paleoenvironmental Studies of the
Department of Geosciences, University of Arizona. The extraction procedure utilized generally followed the standard HCL and HP digestion technique used for alluvial sediments (Martin et aT., 1961; Mehringer, 1967)• This process removes carbonates, silicates, and other inorganic material from the surface samples. Acetolysis was used to remove non-resistant organic material from the samples
(Erdtman, 1943). Following the extraction procedure a drop of the relatively pure pollen matrix was mounted in glycerine and basic fuchin stain on a glass slide. The excess pollen residue derived from the extraction was placed in glass vials and stored. Table 2 shows.the complete sequence utilized in the extraction procedure.
Pollen Analysis
The pollen recovered were identified and tabulated using a Zeiss binocular microscope at 640X. The more
difficult identifications were made under anisole oil
immersion. Pollen identifications were made at the generic
level wherever possible, however generic pollen determina
tions of many of the plant families in the Southwest are not 18
Table 2. Extraction Procedure for Southwestern Alluvial Pollen Samples.*
Approx. 50 g« of sediment
HCL swirl, 750 ml. beaker
#100 mesh brass screen
HCL swirl, 250 ml. beaker
transfer to test tube
10-15# HCL
25-30# HCL H^O wash
50# HP, 24 hour stand
70# HPa 24 hour stand
70# HP, 30 minutes in boiling H^O bath
2 boiling HgO washes
20# HNO^, 10 minutes stand
2 boiling H^O washes
Acetolysis
2 boiling HgO washes
cone. HCL (37#), 2 minutes in boiling H^O bath
2 boiling H^O washes
5-7# NAOH, 2-3 minutes in boiling H^O bath HgO washes until decant is clear
transfer to vial
mount on slides
'*After Mehringer, 1967• 19 possible. No attempt was made to identify the pollen types of Finns, Juniperus, and Quercus past the generic level.
"Cheno-ams" refer to various genera in the family
Chenopodiaceae indistinguishable from the genus Amaranthus of Amaranthaceae. Grass pollen was not identified below the family level. The pollen of the subfamilies Liguliflorae and Tubiflorae in the Compositae are morphologically dis tinct, and the latter subfamily was divided into two artificial pollen types: high- and low-spine Compositae
(Hevly, Mehringer, and Yokum, 1965)•
Low-spine Compositae are generally wind-pollinated and include members of the tribe Ambrosieae, while the high-spine Compositae are generally insect-pollinated and include such genera as Encelia, Zinnia, and Helianthus. The pollen of the genus Artemisia is distinct from that of the Compositae.
The pollen of Ephedra was separated into two artificial groupings: E. torreyana- and E. nevadensis-type as proposed by Martin (1963) and Hevly ofc al. (1965)• In the Grand Canyon the JE. torreyana-type contains only that
species while the nevadensis-type includes both E. viridis and J3. nevadensis.
Two hundred pollen grains were counted on each slide.
No pollen types observed were excluded from the sum. Pollen
counts of each site were plotted in an attempt to illustrate
the relationship of the modern pollen to the vegetation communities and elevation along the traverse (Figure 3).
The relative frequency of the pollen types recovered are presented in Appendix 1. 21
PINUS
JUNIPERUS
QUERCUS
EPHEDRA
GRAMINEAE
COMPOSITAE
ARTEM ISIA
CHENO-AMS
TIM iw jin m ho
■ lu itw m e u s K * iii Mnoe-iuiiiMi QWWOWMO
jumi SHM UM M M
Figure 3* Modern Pollen Spectra of the Grand Canyon, Arizona. MODERN POLLEN DISTRIBUTION
Analysis
Of thirty-five pollen types identified from the surface samples collected in the Grand Canyon area (Appendix
1), the principal ones are: Pirns, Juniperus3 Quercus,
Ephedra, Graminae, Compositae, Artemisia, and Cheno-ams
(Figure 3). These pollen types were present in nearly all the samples and accounted for nearly 90 percent of the total pollen present.
.The arboreal pollen (AP) frequency shows a high positive correlation when plotted against elevation (Figure
4). The AP frequency largely reflects the abundance of
Pinus, and generally exceeds 60 percent of the total pollen present in samples collected in woodland, parkland, and
forest communities. High frequencies of Pinus appear to
coincide with the general distribution of Pinus edulis and
I\ ponderosa in these communities.
Pinus is well represented (10-34$) in most of the
samples collected in the desert shrub community. This
effect points to the importance of long distance, wind blown
transport of Pinus pollen, and strongly suggests the
presence of relatively poor local pollen producers in this
community.
22 70
60
SO
AP 40
(percent) 30
20
10
0
ELEVATION (meters)
Figure 4. Relationship of Arboreal Pollen Frequency to Elevation. 24
The lowest percentage of Finns (10$, N = 400) was found in the sample collected at Plateau Point at an elevation of 1160 meters on the south side of the Canyon.
The Pinus values obtained from surface samples collected approximately 150 meters above and below this site averaged about 27 percent. The relatively sharp decrease of Pinus at Plateau Point may possibly be explained by the topo graphic position of the site or in terms of local vegetation characteristics.
Plateau Point, on the Tonto Shelf, overlooks the
steep escarpment of the Inner Gorge of the Colorado River.
The Tonto Shelf is a narrow surface of relatively little
relief occasionally cut by side canyons leading into the
inner canyon.
The general physical features of the Plateau suggest
the possibility of differential heating between the areas
of exposed flat surfaces and the side canyons. If this
effect were present, convectional updrafts would result over
much of the Shelf during the day. Cold air drainage during
the night would be directed down the side canyons and away
from the exposed surfaces. Because Pinus pollen is highly
bouyant and subject to wind transport, the deposition of
Pinus at Plateau Point may be significantly reduced by
adverse wind patterns. In addition the deposition of Pinus
may be affected through the exposed nature of the Point with
respect to strong inner canyon winds. 25 The vegetation at Plateau Point is characterized by a relatively closed community of blackbrush, with Ephedra torreyana. Yucca sp., and other elements of the desert shrub community. The large population of exclusively non arbor eal pollen producers may be controlling the relative abundance of Pinus drifting in from the upper slopes and rims. The relative frequency of NAP is high (61.4$), and most of these types are relatively less bouyant or are insect-pollinated. The aerodynamics of these pollen types, combined with the low slope declivity of the site, and the closed nature of the vegetation may retard both wind trans port and slope wash movement of the local non-arboreal pollen types from the area.
Several factors or combinations of factors appear to be limiting the frequency of Pinus on Plateau Point. Future studies in either this area of the Canyon, or in areas of similar geographic nature may profit by utilizing absolute pollen frequencies or employing closer spaced sampling procedures.
Other coniferous pollen sporadically present in the surface samples include Picea, Abies, and Pseudotsuga (PAP).
These types were grouped because their combined relative abundance generally never exceeded 1 percent of the total pollen present. Pseudotsuga had the most limited distribu tion, and was found only at the site collected at 1950 meters on the south side and between 1980-2515 meters on the 26 north side. The distribution of this large, heavy pollen type tends to reflect the local occurrence of Pseudotsuga taxifolia on the more mesic north-facing slopes of both rims. The presence of a single Picea pollen grain recovered in a sample collected near the Colorado River and the isolated occurrences of Abies pollen in the desert shrub community further demonstrate long distance, wind transport in the Canyon. The highest frequencies of PAP pollen were found distributed in and directly below the mixed coniferous forest community reflecting the nearness and composition of this community.
The highest frequencies of oak pollen were found distributed above 1525 meters elevation in the pinyon- juniper woodland on the south side of the Canyon, and between 1220-2130 meters on the north side. Small amounts of Quercus (app. 5^) in the pinyon-juniper woodland suggest the presence of Quercus gambelli, which is a subdominant element in this community. High frequencies of oak pollen
(up to 38%) on the north side apparently reflect the increasing presence of generally closed stands of Q. gambelli and its hybrids in the narrowing, more mesic, northwest trending Roaring Springs Canyon. In this canyon the relative abundance of oak pollen sharply declines near the ecotone between oak woodland and the mixed coniferous forest. 27 A sharp decrease in Quercus pollen, accompanied by an abrupt increase in the relative abundance of high-spine
Compositae, occurs at 1830 meters elevation in Roaring
Springs Canyon. The sample was collected in a relatively open pinyon-oak association distributed on a southwest
facing slope. The pollen and vegetation data at this site
suggest that the more xeric slope exposure may be influenc
ing the relative frequency of local non-arboreal pollen producers.
The presence of up to 5 percent Ostrya pollen in the
oak woodland suggests the presence of Ostrya knowltoni which is a local subdominant in this community. Five
Juglans (walnut) pollen grains were found in samples col
lected between 1220-1980 meters elevation on the north side
of the Canyon. These pollen grains are of interest as the
closest known source area for this type is located in
Havasu Canyon approximately 65 kilometers west of the
deposition area (MacDougall, 1947)• Its occurrence here may
indicate a local source somewhere on the north side of the
Canyon.
The distribution of Juniperus is somewhat uniform
throughout the surface samples. In general Juniperus
reaches its maximum abundance in the pinyon-juniper woodland
and juniper shrub savannah communities. Because of the
difficulties encountered in the identification of juniper 28 pollen, the distribution and relative frequency of this type may be somewhat unreliable.
The pollen recovered from the samples collected in the desert shrub community is largely dominated by non- arboreal species. The principal types found in this area are Ephedra and Compositae pollen. The distributions of these types seem to reflect closely the plant species present at lower elevations.
The highest frequencies of Ephedra torreyana-type occur in the samples collected at Plateau Point on the south side of the Canyon, and at 1200 meters elevation on the north side. The abundance of E. torreyana-type is low for most samples collected in the desert shrub community, and is present in trace amounts above 1500 meters on both sides of the Canyon. The distribution of E. nevadensis-type is more consistent, gradually increasing in abundance with decreasing elevation from the rims.
The presence of four acacia polyads in samples distributed in the desert shrub community reflects the occurrence of Acacia greggi. Cat claw acacia is insect pollinated, and produces large, heavy polyads which have a limited distribution.
Low-spine Compositae pollen is evenly distributed throughout the traverse with the highest frequencies found in the desert shrub community. Changes in the relative abundance of this type may reflect variations in the 29 abundance of Franseria sp. The frequency of high-spine
Compositae is greatest in samples collected adjacent to the
Colorado River, and decreases with increasing elevation.
The abundance of high-spine Compositae pollen near the
River is probably related to the local distribution of
Encelia farinosa, Brickellia sp., and Baccharis sp. in this area. High-spine Compositae pollen on the upper slopes of the Canyon appears to be related to the prevalence of
Chrysothamnus sp. and Gutierrezia sp., both subdominants in the juniper shrub savannah and the pinyon-juniper woodland.
The pollen of Gramineae, Cheno-ams, and Artemisia is characterized by relatively low frequencies generally uniformly distributed throughout most of the samples.
Gramineae pollen is more abundant near the rims of the
Canyon and, surprisingly, in the desert shrub community.
This distribution suggests abundance of grass present on the
cooler, more mesic upper slopes. The higher frequencies of
Gramineae in the desert shrub community may point to the
relatively poor local pollen production of many of the
desert species.
An abundance of Cheno-am pollen was noted at 1493
meters on the south side of the Canyon. This sampling site
was collected near a small floodplain of Garden Creek, and
apparently reflects the disturbed nature of the site.
The relative frequency of Artemisia pollen never
exceeded 5 percent abundance in the samples collected in the 30
Canyon, but increased to nearly 23 percent on the Coconino
Plateau in a ponderosa pine-sagebrush community. These data seem to suggest a relatively limited dispersion for
Artemisia pollen in the Canyon.
Consistency of the Data
The results of the present study are compared below with other selected surface pollen studies in the Southwest to determine the general trends of findings. The studies selected for comparison with the Grand Canyon data were chosen from their similar elevational and zonal relation ships .
In a study of southeastern Arizona, Martin (1963) indicated the frequency of arboreal pollen increases in woodland and parkland localities, and non-arboreal and herbaceous pollen generally dominated the lower shrub and grassland communities. The frequency of Pinus was highest in samples collected above l800 meters elevation. High
frequencies of Pinus from desert areas reflected regional mixing from the montane forest sources, and suggested the poor local pollen production of many desert species. The
lower desert areas were generally characterized by high
frequencies of Cheno-ams and high- and low-spine Compositae pollen.
In a study of the Las Vegas Valley, Mehringer (1967)
found a close geographic correlation between the modern 31 pollen composition and the local vegetation communities.
The study indicated desert areas were largely dominated by both low-spine Compositae and Cheno-am pollen. The presence of Pinus was significant in desert areas and was interpreted by Mehringer to be the result of the sparse vegetation cover and locally poor pollen producers.
Woodland communities were dominated by high Pinus,
Juniperus, and Artemisia values closely reflecting the
distribution of these plants.
In Hevly's study (1964) in northeastern Arizona, the
modern plant communities were characterized by a succession
of pollen types with an increasing relative abundance of
arboreal pollen with elevation. Woodland, parkland, and
forest communities were sharply separated from the lower
elevation communities by more than 50 percent arboreal
pollen. The forest and woodland communities were charac
terized by between 50-80 percent Pinus pollen with varying
amounts of Abies, Picea, Pseudotsuga, and Quercus pollen.
Below the woodland areas Cheno-am and Compositae pollen
increased in abundance in the grassland and desert communi
ties . Graminae pollen was more abundant in the desert areas
than in the grasslands, and Hevly suggested this was probably
due to the poor local production of the desert species.
The relationship of the surface pollen to vegetation
communities and elevation in the Grand Canyon area appears
to be in general agreement with the results of the above 32 studies. The abundance of arboreal pollen types in forest and woodland communities closely compares with those found in the other areas. The distribution of non-arboreal pollen types in the study area appears to be related to local distributions of plants in the Canyon. Compared with the other studies, the most significant anomaly in the Grand
Canyon data is the low frequency of Cheno-ams in the desert shrub community. This effect may point to an actual lower abundance of these plants growing in the area due to unfavorable habitats. SUMMARY AND CONCLUSIONS
The modern pollen distribution in the Grand Canyon suggests a close geographic relationship between the vegetation communities and elevation despite the local overrepresentation of coniferous pollen, especially Pinus, in the desert areas. Relatively high frequencies of arboreal pollen (50-70$), mainly Pinus, dominate the surface samples collected in woodland and forest communities. The presence of oak pollen between 5-15 percent in the woodland samples suggests the close proximity of Quercus gambelii.
Higher frequencies of Quercus pollen appear to characterize a relatively closed oak woodland. Sporadic occurrences of
Picea and Abies pollen in the desert samples suggest wind transport, but the highest frequencies of these types occur in and near the mixed coniferous borders.
The juniper shrub savannah community appears to be characterized by somewhat variable frequencies of Juniperus pollen and high frequencies of high-spine Compositae pollen.
The lower desert shrub community is dominated by the high relative abundance of Ephedra and Compositae pollen. Varia tions in the abundance of Compositae pollen appears to indicate local changes in the vegetation associations.
Pinus appears to be significantly overrepresented in most of the samples collected from the desert areas. This
33 34 effect may point to the presence of locally poor pollen producers in the area, and suggests the lower canyon is acting as a huge depositional trap for arboreal pollen drifting in from sources on the upper slopes and rims.
The occurrence and distribution of Acacia polyads in the surface samples suggests this pollen type is a relatively good indicator of the desert communities, a feature not reported by Martin (1963) or Hevly et al. (1965) in southern Arizona.
Sharp variations occurring within relatively homogeneous pollen zones appear to suggest local differences in pollen production related to slope exposure and the topographic position of the site.
While it presents unusual opportunity for atmos pheric mixing of pollen, the Grand Canyon study shows a pattern of change with elevation in accord with other modern pollen studies made across similar vegetation com munities in the Southwest. Major variations in the relative pollen counts appear to be due to local compositional differences in the plant communities.
The pollen data in the Canyon suggest the wind- pollinated type, Artemisia, is especially limited in disper sion. The high frequencies of this pollen type in pre-
12,000 B.P. deposits at Ramparts and Stanton caves suggest
Artemisia was growing in abundance at these sites. APPENDIX 1
MODERN POLLEN FREQUENCIES IN THE
GRAND CANYON, ARIZONA
35 36 (meters) Exposure Pinus Elevation Site No. Slope Abies Vegetation
Park Entrance Sta.
1 Ponderosa- 2255 0° Open 42.0 Sagebrush South Rim
2 Pinyon-Juniper 2103 0° Open 43.0 - O o 3 Pinyon-Juniper 1950 NW 43.0 4 Pinyon-Juniper 1798 45° NW 35-0
5 Ecotone 1645 50° N 38.0 o o CVJ 6 Juniper Shrub 1493 N 29.5 Savannah
7 Juniper Shrub 1340 25° ¥ 29.5 Savannah
8 Ecotone 1250 0° Open 30.0
Plateau Pt.
9 Desert Shrub 1160 0° Open 10.0
10 Desert Shrub 1005 35° NE 25.5
11 Desert Shrub 777 35° S 16.0 o H o 12 Desert Shrub 762 S 16.5 O O 13 Desert Shrub 915 N 29.0 11 13 12 10 6 4 9 7 2 8 5 i 3 5 16.0 .5 Pseudosuga 20.5 15.0 10.0 13-5 11.0 13.0 14.0 704.0 17.0 10.0 15.5 17.0 12.0 •H CD 5 CQ P A h 4.0 1.5 1.5 4.5 1.0 3.5 3.3 1.0 2.5 1.0 3.0 5.0 S 0 CO CD T) O 18.3 2.0 2.0 2.0 1.0 1.5 £ -p & & & cd 0 o .5 .5 .5 .5 • 21.5 29.5 19.0 12.5 11.0 6.0 6.5 6.5 5.5 1.5 3.0 1.0 x: TJ dc •H o cd cd 0 f4 0 C > • 2.0 4.0 3.5 5.5 •H Onagraceae 39 13 11 12 10 61.0 2 4 1 6 3 44.5 7 8 5 9 5 46.5 .5 Nyctaginaceae 64.0 56.5 45.0 60.0 41.5 56.0 28.8 44.0 28.5 32.5 < p -, 41.5 48.0 38.5 39.0 36.6 30.5 52.0 61.4 58.0 64.0 68.8 55• 5 55.5 50.5 g 4.0 7.5 6.0 1.0 5.5 3.5 9-8 3.0 3-5 3.0 -P I • 5 CZ) so • •H O 0 o -P •H W c6 -P ^ P ■P d 0 0 W w 0 0 r* *P Qa o P -p hO 0 0 O A P •H 0 H S H % •H CO > W CO W Ph Picea 14 Desert Shrub 1067 5° w 34.0 ' -5 15 Desert Shrub 1220 0° w 15 .5 °o 16 Ecotone 1340 H w 2 6 .0 Roaring Springs 0 0 CXJ 17 Me sic Community 1432 sw 20.0 .5 18 Pinyon-Juniper 1525 35° E 2 5 .0 Oak Woodland 19 Ecotone 1676 4o° E 2 4 .0 20 Oak Woodland 1830 30° SW 2 3 .5 1 .5 O O 21 Oak Woodland 1980 U1 E 31.0 .5 22 Oak Woodland 2135 50° SE 22.0 .5 23 Ecotone 2286 35° SE 37 .0 • 5 1 .5 North Rim 24 Mixed Conif erous Forest 2515 0° Open 61.0 3-0 2 .5 Meadow, Kaibab Plateau 25 Spruce-Fir 2560 .0° Open 50.0 4 .0 6 .5 Forest 25 24 23 22 21 20 19 18 17 16 14 15 3.0 1.0 1.5 • 5 • 5 Pseudotsuga 21.5 10.0 10.0 14.0 11.0 12.5 17.0 2.0 4.5 9-0 3.5 9-5 •H g C/2 ) 0 U A 25 21.0 25.0 23-5 16.0 17.0 14.0 38.0 31.5 2.0 4.5 1.5 S •H x; Rhamnaceae 42 20 22 14 16 15 17 19 18 23 21 25 3.5 3.0 1.0 5.0 .5 .5 Betulaceae l.o •H P cti 3 X 3 C/3 h 1.0 i h> — •H d CO 0 3 to • .5 • 1 5 5 1.0 < d o O 1.0 . 1.0 1.5 1.0 1 P4 — CO 3 A O .5 • 5 .5 .5 • 5 .5 1 . 1.0 1.5 C < i — 3 CO 3 i • 5 O (D • 5 •H + •H <+H CO cd c6 d O 0) 10.0 H 15.0 2. o 7. 8.0 8.5 8.5 8.0 8.0 8.0 5.5 cb d d CD 3 CD S 43 25 24 20 23 22 21 19 18 17 16 15 14 10.5 2.0 6.0 2.0 2.0 1.5 3.0 3-0 3-5 1.0 . 6.0 5.0 - 8.0 9-0 HS Compositae 10.5 4.5 9-5 4.5 5.0 3-5 5.0 5-5 5-0 3-0 to o •H •p ro d 0) o o 2.5 4.0 . . 2.5 1.0 3.0 5.0 3-0 1.5 . 5.0 5.0 5.0 3-5 •H < •H P 2.0 1.0 1.0 . 1.0 1.0 H P4 cd cd bO C Q) (D k o O O •H rH PU cd cd Opuntia 44 14 15 21 20 17 23 22 16 19 18 25 24 Shepherdia o 5 67.5 •5 d d o 0 ADAM, D. P. 1965 Exploratory Palynology in the Sierra Nevada, California. Unpublished Master’s thesis, Univ. of Arizona. BENNETT, P. S. 1969 Some notes on the Vegetation of the Inner Gorge, Grand Canyon. Four Corners Geological Society, 5th Field Conference. Powell Centennial River Expedition, pp. 25-34. BENT, A. M. and H. E. WRIGHT, Jr. 1963 Pollen Analysis of Surface Materials and Lake Sediments from the Chuska Mountains, New Mexico. Geological Society of America Bulletin 74, pp. 491-500. CLOVER, E. U. and L. JOTTER 1944 Floristic Studies in the Canyon of Colorado River and Tributaries. American Midland Naturalist, 32, p p . 591-642. DAVIS, M. B. 1969 Palynology and Environmental History during the Quaternary Period. American Scientist, 57* p p . 317-332. DIXON, H. N. 1962 Vegetation, Pollen Rain, and Pollen Preservation, Sangre de Christo Mountains, New Mexico. Un published Master's thesis, Univ. of New Mexico. ERDTMAN. G. 1943 An Introduction to Pollen Analysis. Ronald Press, New York. 239 pp. GREEN, C. R. and W. D. SELLERS 1964 Arizona Climate. University of Arizona Press, Tucson, pp. 209-212. HEVLY, R. H. 1964 Pollen Analysis of Quaternary Archaeological and Lacustrine Sediments from the Colorado Plateau. Unpublished Ph.D. dissertation, Univ. of Arizona. 46 47 HEVLY, R. P. J. MEHRINGER, Jr., and H. G. YOKUM 1965 Modern Pollen Rain in the Sonoran Desert. Journal Arizona Academy of Science, 3a PP• 123- T35: KEARNEY, T H. and R. H. PEEBLES I960 Arizona Flora. University of California Press, Berkeley and Los Angeles. 1,085 PP• KING, J. E 1971 A River Level Pollen Transect in the Grand Canyon of the Colorado River. Abstracts. 15th Annual Meeting Arizona Academy of Science, p. 28. MACDOUGALL W. B. 1947 Plants of the Grand Canyon National Park. Grand Canyon Natural History Association Bulletin 10, Grand Canyon, Arizona. MAHER, L. ., Jr. 1963 Pollen Analysis of the Surface Material from the Southern San Juan Mountains, Colorado. Geological Society of America Bulletin, 74, pp. 1485-1504. MARTIN, P. S. 1963 The Last 10,000 Years, a Fossil Pollen Record of the American Southwest. University of Arizona Press, Tucson. 87 pp. MARTIN, P. S. (n.d.) Trees and Shrubs of the Colorado River through the Grand Canyon: Lee's Ferry to Diamond Creek. In preparation. Dept, of Geosciences, Univ. of Arizona, Tucson. MARTIN, P. 5., B. SABELS and D. SHUTLER 1961 Rampart Cave Coprolite and the Ecology "of the Shasta Ground Sloth. American Journal of Science, 259i PP- 102-127. MARTIN, P. 5., J. SCH0ENWETTER and B. C. ARMS 1961 Southwestern Palynology and Pre-history. Mimeo graphed. Geochronology Laboratories, University of Arizona. 118 pp. MEHRINGER, P. J. 1967 "Pollen Analysis of the Tula Springs Area, Nevada," pp. 130-200. in H. Wormington and D. Ellis (eds.), Pleistocene Studies in Southern Nevada. Nevada State Museum. Anthropological Papers, no. 13, Carson City. 48 MERKLE, J. 1952 An Analysis of a Pinyon-Juniper Community at the Grand Canyon, Arizona. Ecology, 33, pp. 375-384. MERKLE, J. 1954 An Analysis of the Spruce-Fir Community on the Kaibab Plateau, Arizona. Ecology, 35, pp. 316-322. MERKLE, J. 1962 Plant Communities of the Grand Canyon Area, Arizona. Ecology, 43, pp. 698-7IO. MERRIAM, C. H. I89O Results of a Biological Survey of the San Fran cisco Mountain Region and the Desert of the Little Colorado in Arizona. North American Fauna, 3, Department of Agriculture, Washington, D.C., 128 pp. POTTER, L. D. and J. ROWLEY I960 Pollen Rain and Vegetation, San Augustin Plains, New Mexico. Botanical Gazette, 122, pp. 1-25. RAND, P. J. 1958 The Plant Communities of the Grand Canyon National Park, Arizona. Proc. Minnesota Acad. Science, 26, pp. 88-90. RASMUSSEN, D. I. 1941 Biotic Communities of the Kaibab Plateau, Arizona. Ecological Monographs, 11, pp. 229-275. SCHWARTZ, D. W., A. L. LANGE, and R. de SAUSSURE 1958 Split Twig Figurines in the Grand Canyon, Arizona. American Antiquity, 23, pp. 264-274. (R. Y. Anderson cited in this report for a preliminary pollen analysis of Tse-an-Kaetan Cave in Cremation Canyon.) STRAHLER. A. N. 1944 Valleys and Parks of Kaibab and Coconino Plateaus, Arizona. Journal of Geology, 52, pp. 36I-387. () i i 0 . 64 16